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Synthesis 2004(9): 1457-1465  
DOI: 10.1055/s-2004-822367
PAPER
© Georg Thieme Verlag Stuttgart · New York

A New Route to Enol Ethers

Takeshi Takeda*, Kensaku Sato, Akira Tsubouchi
Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
Fax: +81(42)3887034; e-Mail: takeda-t@cc.tuat.ac.jp;
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Publication History

Received 9 April 2004
Publication Date:
10 May 2004 (online)

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Abstract

Dithioorthoformates having various alkoxy groups were obtained by copper(II) bromide-promoted oxidative coupling of bis(phenylthio)methyltributylstannane with alcohols. The dithioorthoformates thus prepared are useful precursors for alkoxymethylidene complexes of titanium, which transform carbonyl compounds into a variety of enol ethers. Even the alkoxymethylidene complexes having a terminal olefin moiety can be prepared and employed for carbonyl olefination without formation of ring-closing metathesis product.

Key words

carbene complexes - esters - ketones - olefination - titanium

16

Titanocene alkoxymethylidenes are also unreactive toward intermolecular reaction with olefins. Thus the treatment of dithioorthoformate 2a with 3 in the presence of 4-phenyl-but-1-ene gave the olefin metathesis product, 1-benzyloxy-4-phenyl-but-1-ene, in only less than 8% yield.